diff --git a/src/grammar.y b/src/grammar.y
index 94fd0a9..352c2ea 100644
--- a/src/grammar.y
+++ b/src/grammar.y
@@ -196,7 +196,7 @@ function_declaration:
 idlist:
           ID {
               TableNode *entry = getFirstEntry(cur);
-              while (getName(entry) != NULL) {
+              while (strcmp(getName(entry),"undefined") != 0) {
                   entry = getNextEntry(entry);
               }
               if (getNextEntry(entry) == NULL) {
@@ -207,7 +207,7 @@ idlist:
         | ID {
               
               TableNode *entry = getFirstEntry(cur);
-              while (getName(entry) != NULL) {
+              while (strcmp(getName(entry),"undefined") != 0) {
                   entry = getNextEntry(entry);
               }
               if (getNextEntry(entry) != NULL) {